1. Field of the Invention
The present invention relates to a melt-blown non-woven fabric. More specifically, the invention relates to a melt-blown non-woven fabric obtained by using an ethylene-.alpha.-olefin copolymer having a particular low crystallinity or a resin composition of a combination of this ethylene-.alpha.-olefin copolymer and other resins.
The melt-blown non-woven fabric of the present invention has a feature in that it has excellent softness. In particular, the former melt-blown non-woven fabric obtained by using substantially an ethylene-.alpha.-olefin copolymer having a particular low crystallinity is rich in elasticity and has excellent fitness, and the latter melt-blown non-woven fabric obtained by using a resin composition of a combination of the above ethylene-.alpha.-olefin copolymer and another resin such as a polypropylene exhibits particularly excellent heat-workability.
The present invention is further concerned with a laminated non-woven fabric material using the above melt-blown non-woven fabric.
2. Description of the Prior Art
A melt-blown non-woven fabric is obtained by extruding a molten resin to form fine resin streams which are then brought into contact with a heated gas of a high speed thereby to obtain non-continuous fibers of fine diameters, and integrating the fibers on a porous support material. The melt-blown non-woven fabric has a relatively soft property and is used for such purposes as clothing and medical supplies.
In such applications, however, the melt-blown non-woven fabric by itself lacks the strength, and means has been employed to reinforce the non-woven fabric by sticking such as of a spun-bonding method or any other method.
For instance, Japanese Patent Publication No. 11148/1985 (corresponds to GB1453447) and U.S. Pat. No. 4,041,203 disclose a non-woven fabric material comprising a web of substantially continuous filaments which have an average filament diameter of greater than about 12 microns and are deposited in a random fashion and are molecularly oriented, and an integrated mat of a largely non-continuous thermoplastic polymeric micro fiber having an average fiber diameter of smaller than about 10 microns and a softening point which is lower by about 10.degree. C. to 40.degree. C. than the softening point of the continuous filaments, wherein the web and the mat are arranged maintaining a laminar relationship and form discretely coupled regions upon the application of heat and pressure.
In producing the non-woven fabric from the polypropylene fiber, furthermore, it has long been known to use a fiber having a low melting point as a so-called binder fiber. For instance, according to Japanese Laid-Open Patent Publication No. 179246/1986, there has been described that a fiber comprising a blend of 65 to 95% by weight of a low-density polyethylene and 5 to 35% by weight of a polypropylene exhibits superior melt-spinnability to that of a polyethylene, and is suited for being used as a binder for the non-woven fabrics. Moreover, Japanese Laid-Open Patent Publication No. 175113/1988 discloses the use of a blend which comprises 99 to 50% by weight of a linear low-density polyethylene that is a copolymer of an ethylene and an octene-1 (1 to 15% by weight), and 1 to 50% by weight of a crystalline polypropylene.
Moreover, Japanese Patent Laid-Open Publication No. 303109/1988 discloses a non-woven fabric of a blended structure obtained by melt-spinning a composition comprising 99 to 50% by weight of a linear low-density polyethylene which is a linear low-density copolymer of an ethylene and at least one kind of an .alpha.-olefin with 4 to 8 carbon atoms and substantially containing this .alpha.-olefin with 4 to 8 carbon atoms and substantially containing this .alpha.-olefin in an amount of 1 to 15% by weight, having a density of from 0.900 to 0.940 g/cm.sup.3, a melt index of 25 to 100 g/10 min. (as measured in compliance with the method of ASTM D-1238(E)), and a heat of fusion of 25 cal/g or greater, and 1 to 50% by weight of a crystalline polypropylene having a melt flow rate of smaller than 20 g/10 min. (as measured in compliance with the method of ASTM D-1238(L)).
However, although the melt-blown non-woven fabric obtained from a single thermoplastic resin material such as a polypropylene or the like may exhibit superior softness to the non-woven fabrics of the other types, it still must have particularly excellent elasticity and fitness in addition to the softness when it is used in such applications as clothing, medical supplies, hospital supplies and the like.
Even in the field of cleaning materials, furthermore, it is desired to further improve the softness from the standpoint of fitness to the surfaces to be wiped and adsorption of dust and dirt.
For example, the cataplasm is stuck to an elbow or a knee under a condition where it is slightly bent. However, the cataplasm which uses the currently available non-woven fabric as a base material has its base material deviated without expanded when the hand or the leg is deeply bent or, on the other hand, has its base material greatly wrinkled when the hand or the leg is stretched, causing the medicine to be leaked.
Examples of the currently available elastic fiber materials include spandex yarns and other rubber yarns which, however, are generally expensive and cannot be processed into such a non-woven fabric as a melt-blown non-woven fabric. Thus, there has not yet been provided a non-woven fabric that is rich in elasticity and that exhibits fitness in various applications.
Moreover, heat resistance and mechanical strength are, in many cases, required in combination in addition to softness in such applications as clothing, medical supplies, etc. In order to obtain a non-woven fabric that meets such objects, therefore, means have heretofore been employed to use a fiber having a low melting point as a so-called binder fiber in producing the non-woven fabric from, for example, the polypropylene fiber.
In the non-woven fabric of this kind, however, the binder fiber that bonds to the fiber which carries stress of the non-woven fabric must have a low melting point giving disadvantage from the standpoint of heat resistance of the non-woven fabric thus weakening he cohesive force of the resin which constitutes fibers, i.e., weaking the strength of the non-woven fabric. Moreover, in a process for integrating the non-woven fabric such as by heat-embossing, the processing conditions such as temperature, pressure, processing rate, etc. have small allowance which is not yet satisfactory from the standpoint of workability.